It is sometimes desirable to mount a pocket calculator on the user's forearm. The prior art teaches two ways of doing this. First, the calculator may be strapped to the forearm as in the case of a wrist watch; however this exposes the calculator to dust and the elements of nature especially when worn by an engineer working at a construction site. Secondly, a calculator may be supported in a casing which is strapped to the forearm; however this prevents use of the calculator without removing it from the casing. With either of the above prior art arrangements, the calculator is in an inconvenient position if and when placed on a horizontal surface such as a desktop.